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In years 1999-2001 a scientific experiment with two cultivars of celery, ‘Zefir’ and ‘Helios’ was carried out. We traced the changes of the content and composition of essential oil comprised in leaves, taking into account the length of vegetation period of the above plants. It appeared that the biggest amount of essential oil was contained in the youngest leaves: 0.34% (‘Zefir’ cv.) and 0.30% (‘Helios’ cv.). It was also observed that he older plants in the moment of their collection, the lower content of essential oil. With help of chromatographic analysis the experiment allowed to indicate three fractions: monoterpene, sesquiterpene and phtalid fraction. Limonene appeared to be a dominant component of essential oil obtained from celery leaves independently of the collection date.

Factors influencing the mass change and chemical composition of a plant during its vegetation are numerous, various and often overlapping. Genetic, ontogenetic and environmental variability that involves for example climatic conditions is the main reason for the crop variability as well as for the content of biologically active substances. Those factors that operate after the collection, especially the conditions of drying, and the storage of the material are also important variability factors.

The knowledge of scope and direction of the influence of particular variability factors enables to operate the production processes and obtain both satisfactory crops and high content of biologically active substances. It also allows to obtain desirable stability of chemical composition of material [3, 5].

The presented results are the continuation of systematic experiments on crops, content and composition of compounds that are secondary metabolites occurring in celery. The experiments are carried out at the Department of Vegetable Crops and Medicinal Plants at Agricultural University in Lublin.

The aim of this paper was to trace the changes of the content and composition of essential oil that take place in leaves of two varieties of celery, ‘Zefir’ and ‘Helios’, taking into account the length of vegetation period of the above plants.

MATERIAL AND METHODS

Field examination was carried out in years 1999-2001 on experimental fields of the Department of Vegetable Crops and Medicinal Plants, Agricultural University in Lublin.

The seedling of two varieties of celery was planted 10th May every year of the experiment. The collection of plants took place after 80, 100 and 120 days of vegetation in field. Aerial leaves of two cultivars of celery (Apium graveolens L. var. dulce Mill./Pers.), ‘Zefir’ and ‘Helios’, dried at temperature 28°C. Water content and essential oil content was indicated in aerial leaves in the Deryng apparatus (according to Polish Pharmacopoeia [4]).

Qualitative and quantitative composition of particular components of essential oil was indicated by GC/MS method using ITS-40 apparatus (GC/ITMS system, Finnigan MAT, USA) and DB-5 column: length: 30 m, diameter: 0.25 mm, thickness of stationary phase film: 0.25 µm (J & W, USA). The temperature of the dispenser was 280°C. The temperature gradient was applied (35°C for 2 min, and next the growth for 4°C up to 280°C).

The qualitative analysis was carried out on the basis of MS spectra which were compared with the NIST spectra (62000) and LIBR spectra of terpenes supplied by Finnigan MAT. The identity of the compounds was confirmed by retention indexes taken from literature or our own data [7]. The quantitative content of essential oil was described assuming that the sum of particular oil compounds is 100%.

RESULTS

Table 1 presents the proportional content of water and essential oil in leaves of celery varieties depending on the length of vegetation in field. During the whole experiment, the content of essential oil depended on the plant variety and the length of plant vegetation in field. It was indicated that ‘Zefir’ cv. contains a little more essential oil in comparison to ‘Helios’ cv.

It was proved that the amount of essential oil in leaves in two varieties examined decreased directly proportional to the length of vegetation period for the plants in field. The biggest amount of essential oil was obtained from the youngest leaves of two cultivars (average 0.37% for ‘Zefir’ and 0.31% for ‘Helios’), and the collection of the material took place after 80 days. The oldest leaves collected after 120 days of vegetation contained the smallest amount of essential oil (0.22% and 0.11% respectively). Independently of the cultivars and the length of vegetation period of plants in field, the biggest amount of essential oil was observed in 1999 (average 0.36% for ‘Zefir’ and 0.26% for ‘Helios’). The smallest amount of essential oil was indicated in leaves in 2000 (0.22% and 0.16% respectively).

Table 1. Comparison of proportional content of water and essential oil in leaves of two celery cultivars in years 1999-2001

Cultivars

Years of experiment

Water content
%

Essential oil content
%

Length of vegetation period for plants in field (days)

80

100

120

average

80

100

120

average

Zefir

1999

9.12

9.43

9.67

9.41

0.44

0.36

0.28

0.36

2000

9.35

9.57

9.78

9.57

0.30

0.20

0.15

0.22

2001

9.27

9.34

9.41

9.34

0.37

0.30

0.24

0.30

average

9.25

9.45

9.62

9.44

0.37

0.29

0.22

0.29

Helios

1999

9.28

9.50

9.70

9.49

0.37

0.26

0.15

0.26

2000

9.42

9.59

9.87

9.63

0.27

0.15

0.07

0.16

2001

9.36

9.58

9.74

9.56

0.30

0.18

0.11

0.20

average

9.35

9.56

9.77

9.56

0.31

0.20

0.11

0.21

On the basis of the analysis of essential oil from the leaves of both cultivars carried out with GC/MS method, the presence of 27 chemical compounds in essential oil obtained from leaves of ‘Zefir’ cv. and 22 chemical compounds for ‘Helios’ cv. were confirmed. 25 and 22 chemical compounds were identified for ‘Zefir’ and ‘Helios’ variety respectively.

As it results from our experiment, isoprenoids (among them monoterpenes, sesquiterpenes and phtalides) are the main components of essential oil obtained from the examined material (tab. 2).

α- and β-pinene, mircene and limonene belong to the composition of the monoterpene fraction. Limonene is the most important component of this fraction. Its content ranges from 20.4% to 62.7% for ‘Zefir’ cv., and from 15.3% to 57.9% for ‘Helios’ cv., and it depends on the length of the vegetation period of plants in field. α- and β-pinenes ranging from 0.7% to 2.8% for ‘Zefir’ cv. and from 0.3% to 1.8% for ‘Helios’ cv. are another component of the monoterpene fraction. For mircene, the content ranges from 0.4% to 3.4% (‘Zefir’), and from 0.3% to 10.0% (‘Helios’)

Among sesquiterpenes, the presence of β-selinene, β-cariofilene, α-selinenu and cariofilene oxide was confirmed. β-selinene, whose content ranges from 1.1% to 7.5%, (‘Zefir’) and from 0.8% to 2.5% (‘Helios’), and depends on the date of leaf collection, is a dominant compound of the sesquiterpene fraction. Another fraction that appears in essential oil distilled from the examined material is the phtalid fraction where 3-n-butylophtalid, sedanolid, cis- and trans-sedanolid can be found.

Phtalides are usually hardly-volatile with vapour and their content in essential oil depends on the type and variety of the examined material. It should be emphasised that the essential oil occurring in leaves of the examined plants has the biggest content of limonene in the material collected after 120 days of vegetation (in September). On the contrary, the content of 3-n-butylophtalid was the highest in leaves collected after 80 days of vegetation. Higher content of sedanolid, as well as cis- and trans-sedanolid, especially in leaves of ‘Zefir’ cv., deserves particular attention.

DISCUSSION

Essential oil that gives specific flavour to the plants is one of the most important biologically active components occurring in plants from the Apiaceae family. As the result of the experiments carried out in three-year-old experimental cycle (1999-2001) it was indicated that the content and composition of essential oil changed both during the vegetation period and in particular years of celery growing. The results of the experiments on the content and composition of essential oil found in literature concentrated around celeriac/knob celery. The content of essential oil in the root ranges from 0.18% to 0.25%. In leaves, it ranges from 0.10% to 0.23%. Limonene, β-selinene 3-n-butylophtalid and sedanolid occurs in this essential oil [8]. The experiments carried out by Wolski et al. [6] concentrated around the content and composition of essential oil occurring in celery fruits. Monoterpenes, sesquiterpenes and phtalides that give characteristic smell to celery fruit, roots, herbs and the products obtained from these components, are dominant elements of essential oil distilled from the fruits of the celery [1].

The experiments carried out on celery leaves indicated that essential oil in leaves contains mainly monoterpenes (α-and β-pinene, mircene and limonene), sesquiterpenes (β-selinene, β-cariofilene, α-selinene and oxide) and phtalides occurring in essential oil in small amounts because of their hard volatility with water vapour [2, 8].

CONCLUSIONS

The biggest amount of essential oil was contained in the youngest leaves: 0.34% (‘Zefir’ cv.) and 0.30% (‘Helios’ cv.). The older plants in the moment of their collection, the lower content of essential oil.

The proportional content of essential oil obtained by distillation with water vapour from the leaves of two celery cultivars depended on the leaf age and ranged from 0.34% (after 80 days of vegetation), from 0.24 to 0.28 (after 100 days of vegetation), and from 0.17 to 0.20% (after 120 days of vegetation in field).

Three fractions: monoterpene, sesquiterpene and phtalide were indicated as the result of chromatographic analysis. Limonene is a dominant component of essential oil obtained from celery leaves independently of the collection date.

The increase of the content of particular components of essential oil was directly proportional to the length of vegetation period of plants in field. Leaves collected after 120 days of vegetation (in both cases examined) had more limonene and mircene in comparison to those collected after 80 days of vegetation in field.

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